This invention relates to the preparation of carboxylic acid salts, and more particularly, relates to a method for the preparation of carboxylic acid salts by the reaction of primary alcohols with an alkali metal hydroxide in the presence of a copper catalyst.
Carboxylic acid salts are useful in various applications. The salts can be neutralized to the corresponding acid which is also useful in a number of applications, such as a raw material for pharmaceuticals, agricultural chemicals and pesticides. Many of such carboxylic acids are available commercially in large quantities.
U.S. Pat. No. 4,782,183 to Goto et al. discloses a method for the manufacture of amino carboxylic acid salts which comprises subjecting an amino alcohol to an alkali metal hydroxide in the presence of a Raney copper catalyst.
In a patent application published by WIPO as WO 92/06069 on Apr. 16, 1992, a process is disclosed for producing glycine, iminodiacetic acid and nitrilotriacetic acid salts by contacting monoethanolamine, diethanolamine or triethanolamine with an alkali metal hydroxide in the presence of a Raney copper catalyst, wherein at least some of the Raney copper catalyst has been rejuvenated by treating the catalyst under reflux conditions with formic acid (attorney docket No. 39-21 (3145)).
A journal article "Structure and Activity of Chromium-Promoted Raney Copper Catalyst for Carbon Monoxide Oxidation" by Laine et al., Applied Catalysis, 44 (1-2), pages 11-22, discloses that chromium-promoted Raney copper catalysts were prepared, and their activity for the oxidation of carbon monoxide was measured. The surface area of the Raney copper catalyst was directly related to the aluminum content in the precursor alloy and to a lesser extent to the presence of chromium. Bulk cuprous oxide and cupric oxide were detected by X-ray diffraction in the Raney copper catalyst. The presence of chromium inhibited the formation of cupric oxide but not of cuprous oxide. The activity decreased as chromium content increased.
U.S. Pat. No. 4,810,426 to Fields et al., discloses a process for the production of N-phosphonomethylglycine by oxidizing N-phosphonomethylethanolamine or the cyclic internal ester thereof with an excess of an aqueous alkali and a copper catalyst, and thereafter heating at a temperature between 200.degree. and 300.degree. C. Thereafter, the salt is neutralized with an acid to produce the desired N-phosphonomethylglycine.
Although satisfactory results are achieved by the processes of the prior art to convert an alcohol to a carboxylic acid using a copper catalyst, or even a Raney copper catalyst, it has been found that upon repeated usage of the copper catalyst, the activity of the catalyst decreases. Now, it has been found, in accordance with the teachings of the present invention, that the activity of the Raney copper catalyst can be extended to a significant degree, permitting more economic utilization of the catalyst, to convert any number of alcohols to the corresponding carboxylic acid.